Google Chrome: Adblock Plus has long been a great extension for toning down ad-infested sites, and the newest version can even block in-video ads so you don't need to wait around to watch YouTube.

Video blocking isn't available in the stable version of Adblock Plus yet, but you can grab the experimental version now to try it out. Before you install, you'll need to head to chrome://flags and enable the "Experimental Extension APIs" flag. Then, scroll to the bottom of the page and hit "Relaunch Chrome". Once you've relaunched, the extension should install as normal. Unfortunately, since the add-on is still in the experimental stages, it doesn't work on every video player—in fact, at the moment, it looks like it only works on YouTube (Hulu, CBS, NBC, and other TV players were unfortunately immune). Hopefully, though, as they continue to tweak the new version, it'll be able to block other video players as well.

Adblock Plus is a free download for Google Chrome. The Firefox version of Adblock Plus doesn't have this feature, but you can install the Adblock Video extension to block embedded ads in videos.